Higher Disturbances of Movement in Monkeys (Macaca Fascicularis)

Abstract

Flexibility in being able to perform the appropriate action to the external situation constitutes a necessary condition for survival; without this ability the animal and man would fail to adjust to the specific demands of their external environment. But little is known of the brain mechanisms that allow the animal and man to choose the appropriate movement according to the external situation with which they are presented. There are neurological patients with damage to the frontal cortex who have great difficulty in carrying out purposeful movements without paralysis or a primary motor defect (normal strength, reflexes, coordination). Liepmann (1900) first described patients with lesions that included the frontal lobe and who demonstrated an inability to execute sequences of movements. He termed this deficit ‘apraxia’. But although apraxia following frontal lobe damage was reported by many investigators (e.g., Botez, 1974; Denny-Brown, 1958; Kolb and Milner, 1981), it has not yet proved possible to identify a critical region in the frontal cortex in the work with patients. This is due to the fact that cortical damage in patients rarely affects a single functional or anatomical entity of the brain; consequently, it is difficult to correlate a particular deficit with the loss of a particular structure or area. Therefore in the present study higher movement disorders were investigated in a species where the experimenter can make surgical lesions in precisely defined regions of the frontal cortex.